<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let qiyou = prompt("请输入汽油种类");
        let num = Number(prompt("请输入汽油数量"));
        if (qiyou == 92) {
            if (num < 20) {
                alert(`每升${qiyou}汽油6元，共计${num * 6}元`);
            } else {
                alert(`每升${qiyou}汽油5.9元，共计${num * 5.9}元`);
            }
        } else if (qiyou == 97) {
            if (num < 40) {
                alert(`每升${qiyou}汽油7元`)
            } else {
                alert(`每升${qiyou}汽油6.5元`)
            }
        } else {
            alert("不存在此种汽油")
        }
    </script>
</body>

</html>